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Origin of life

ICSE · Class 12 · Biology

Quick revision notes for Origin of life — ICSE Class 12 Biology. Key concepts, formulas, and definitions for last-minute revision.

59 questions37 flashcards5 concepts

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Key Topics to Revise

1

Universe and Origin of Solar System

  • The universe originated 10-20 billion years ago through the Big Bang theory - a massive explosion of tightly condensed matter
  • After the Big Bang, the universe expanded and cooled, leading to formation of hydrogen and helium gases
  • These gases condensed under gravity to form galaxies - approximately 100,000 million galaxies exist in the universe
2

Theories of Origin of Life

  • Theory of Special Creation: Life was created by a supernatural power; all organisms appeared in their present form; based on religious faith, not scientific evidence; cannot be tested scientifically
  • Theory of Spontaneous Generation (Abiogenesis): Life originated from non-living matter without intervention of living organisms; supported by ancient civilizations and philosophers like Aristotle, Van
  • Francesco Redi's Experiment (1668): Disproved spontaneous generation using sealed and uncovered jars with cooked fish; maggots appeared only in uncovered jars proving they come from fly eggs
3

Oparin-Haldane Theory and Eight Steps of Life's Origin

  • Proposed by Russian biochemist Aleksander I. Oparin (1924) and English biologist J.B.S. Haldane (1929); also called abiogenic theory or modern theory
  • Life originated gradually through chemical and physical changes, not suddenly
  • Step 1 - Origin of Earth and Primitive Atmosphere: Earth formed 5-6 billion years ago (some sources say 4.5 billion); initially a fiery spinning ball of hot gases and vapors; gradually cooled over hun
4

Miller-Urey Experiment

  • Conducted in 1953 by American scientist Stanley Miller and Harold C. Urey
  • Classical experiment that experimentally proved the Oparin-Haldane concept of life's origin
  • Recreated probable conditions of primitive Earth in laboratory setting

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Full Notes

Key Concepts

The universe originated approximately 10This theory proposes that all lifeAn ancient theory suggesting that lifeThe theory that life can onlyProposed independently by Russian biochemist Aleksander

Frequently Asked Questions

What are the important topics in Origin of life for ICSE Class 12 Biology?
Key topics in Origin of life include Origin of Life — Complete Concept Map, Experiments Disproving Spontaneous Generation — Timeline, Chemical Evolution to First Life — Complete Pathway. These are the concepts ICSE Class 12 examiners draw on most — study them first, then practise related questions.
How to score full marks in Origin of life — ICSE Class 12 Biology?
Understand the core concepts first, then work through the 59 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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